The present invention pertains to a book binding machine for processing book blocks with a transport system that features a plurality of book block clamps for receiving the book blocks that can be continuously moved along a closed circulation path and are coupled to a traction mechanism, wherein the traction mechanism revolves around a driving wheel and a deflection wheel and is tensioned by means of a tensioning device, and wherein processing stations are arranged in the region of straight sections of the circulation path.
A book binding machine of this design in the form of a so-called perfect binding machine is described, for example, in DE 198 46 525 A1. In this case, book blocks that are loosely gathered from sheets and/or folded sections are transported in the book block clamps of the transport system with a defined overhang and connected into a book block by applying glue on the processed book block spine. A cover feeding and pressing device connects an optionally grooved cover to the book blocks, wherein the cover is pressed against the book block spine, as well as adjacent lateral regions, during the continuous movement of the book blocks.
The drive of the traction mechanism with the book block clamps is realized with a driving motor that is placed on the bottom of the frame such that its output shaft is aligned horizontally, wherein this driving motor is connected to the driving wheel of the transport system by means of different driving elements with inherent play and elasticity, such as transmission gears and angular gears, shafts, belts and/or chains, and also drives various processing stations including the infeed and delivery devices via a main shaft that longitudinally extends in the perfect binding machine.
Due to the transverse connections with the book block clamps guided along the circulation path, the traction mechanism needs to be tensioned by displacing the deflection wheel or the driving wheel longitudinally referred to the straight sections of the circulation path. Due to the drive train leading to the driving wheel, the tensioning process is realized with the non-driven deflection wheel in known perfect binding systems and therefore limits the design options with respect to the arrangement of the driving and deflection wheels relative to the circulation path and assigned processing stations.
With respect to the quality of individual processing steps, it is important that the book block clamps are situated in defined positions at certain times. However, the traction mechanism that consists, for example, of a chain in connection with the elasticity of the drive train between the driving motor and the traction mechanism forms an oscillatory system, wherein the high mass of the traction mechanism with the book block clamps causes this oscillatory system to have low resonant frequencies that can be stimulated by interfering influences occurring periodically with the machine cycle. Consequently, positional errors that vary from book block clamp to book block clamp occur at the respective locations during the oscillation of the traction mechanism, wherein these positional errors can no longer be completely compensated with corresponding countermeasures in the processing stations. The oscillations of the traction mechanism result in higher driving torques on the traction mechanism drive that reduce the service life of the traction mechanism.
A book binding machine of the above-described design is known from DE 102 21 542 A1, wherein the transport system of the book block clamps and at least one processing station can be driven independently of one another in this book binding machine. In order to control this processing station in the sense of a positioning task, a measuring system for determining the position of the respective book block clamp or book blocks is provided in the vicinity of this processing station. The complete drive system is divided into partial systems that are less susceptible to oscillations and the various processing tasks can be carried out much more accurately due to the position measurement in the region of the processing station. However, an elastic drive train still exists between the driving motor and the driving wheel of the traction mechanism.